Liquid crystal display (LCD) devices are gaining widespread popularity due to their small form factors and low power consumption. A LCD device usually includes a circuit board, a backlight module, and a LCD panel. The circuit board drives the backlight module and the LCD panel. The backlight module provides illumination for the LCD panel. The LCD panel presents texts and images. The circuit board usually includes a DC voltage conversion circuit converting a first voltage into a second voltage, and providing the second voltage to the VGH line of the LCD device's Wire On Array (WOA). When conducting Electrical Over Stress (EOS) test on the DC voltage conversion circuit, the VGH line, components of the DC voltage conversion circuit, or components of the LCD device are often burnt down as the DC conversion circuit lacks proper protection mechanism.